The Promise to keep bugged because Frost is dead. how can I fix this without Loading a previous file?

In The Promise to Keep it seems to be bugged as Frost died and I still get asked for Frost despite being dead.

Is there any command I can use to fix this? I can't cannot go back in time via loading a saved file because I've done so many quests >.< between this and my last save.

A quote from the wiki:

To revive Frost after he is dead one can type prid 97E1F then resurrect. It is possible to also open the console and click on Frost's dead body, then type resurrect. This may however result in selecting the wrong target.

If you want to open the console, press the ` / ~ key.

Source: Elder Scrolls Wikia > Frost (Horse)